Synthesis, Crystal Structure and Photocatalytic Properties of a Supramolecular Assembly Based on Keggin Polyoxotungstate

A new supramolecular compound （4,4＇-bipyH）4[SiW12O40]（4,4＇-bipy） （4,4＇-bipy = 4,4＇-bipyridine） was synthesized hydrothermally and characterized by single-crystal X-ray diffraction and IR spectrum. The crystallography analysis for the title compound reveals that the crystal crystallizes in monoclinic, space group C2/m with a = 22.2767（12）, b = 21.1879（11）, c = 15.6942（8） A, β = 97.068（3）°, V = 7351.3（7） A3, Cs0H44N10040SiW12, Mr = 3659.24, Z = 4, Dc = 3.306 g/cm3, F（000） = 6544, GOOF = 1.137, R = 0.0577 and wR = 0.1579. The title compound consists of a discrete Keggin-type [SiWl2O40]4- anion, one 4,4＇-bipy and four protonated （4,4＇-bipyH）＋ cations. The [SiWl2O40]4- anion and protonated 4,4＇-bipy are connected to form a supramolecular structure by hydrogen bonds. Meanwhile, the title compound exhibits good photocatalytic activity for color degradation of Rhodamine-B dye solution under visible-light irradiation.

Comparing the Structures of Two Allomorphic Polyoxotungstates and the Difference in Weak Interactions by Thermal-dependent 2D-COS IR to Identify

A three-dimensional （3D） Keggin-type heteropolytungstate{Zn（phen）3}3[ZnW12O40]·9H2O 1 （phen = 1,10-phenanthroline） has been synthesized through a conventional hydrothermal synthesis and was characterized by X-ray single-crystal diffraction analysis, X-ray powder diffraction （XRD）, IR, UV-DRS, thermogravimetric analysis （TGA）, thermal-dependent 2D-IR correlation spectroscopy （2D-COS IR） and Raman spectrum. Crystal data for compound 1： trigonal system, space group R3 with a = b = 25.268（4）, c = 17.462（5） A, ）, = 120°, V= 9655（4） A3 and Z = 3. Compound 1 is allomorphic to {Co（phen）3}3[CoW12O40]·9H2O 2, which has been reported by Feng Chai et al. In compound 2, its prominent feature is that the decisive role of water molecules （O-H…O） builds a 3D supramolecular structure. However, in the structure of compound 1, the interlayer space is filled by Zn（phen）3]2＋ cations which linked the layers via C-H…O hydrogen bonding interactions to construct a three-dimensional framework. Two compounds are different in weak interactions, so we identify them by Thermal-dependent 2D-COS IR. Moreover, the fluorescence of compound 1 was also described.

Preparation and Photocatalytic Behaviors of Nanoporous Polyoxotungstate-Anatase TiO_2 Composites

Nanoporous anatase TiO2 crystalline particles coupled with Keggin or Wells-Dawson unit, H3PW12O40/TiO2 or H6P2W18O62/TiO2, were prepared at a low temperature （200℃ ） using sol-gel method combined with hydrothermal treatment at programmed temperature. The as-prepared composites have uniform anatase phase, and they exhibit both micrand mesoporosities with pore sizes of 0.6 and 4.0 nm, respectively, and their average size is lower than 10 nm. Photocatalytic tests show the composites exhibit relatively higher photocatalytic activities to decompose the organocholorine pesticide hexachlorobenzene（HCB） than anatase TiO2, the starting polyoxotungstates, and EuEOa/TiO2 prepared by using sol-gel method, and this was attributed to （ 1 ） the synergistic effect of photoactive anatase TiO2 with the polyoxotungstate, and （2） the fascinating physical and chemical properties of the porous materials.

Hydrothermal Synthesis and Structure of a Mixed-valence Polyoxotungstate Decorated by Copper(I) Coordination Group, [Cu(en)_2H_2O]_2[{Cu(en)_2}HPW_(12)O_(40)]·2H_2O

A complex [Cu(en)2H2O]2[{Cu(en)2}HPW12O40]?2H2O (C12H57Cu3N12O44PW12, Mr = 3501.49) has been synthesized under hydrothermal conditions and its crystal structure was determined by X-ray diffraction. It crystallizes in the orthorhombic system, space group Pbca with a = 21.680(4), b = 20.680(4), c = 26.120(5) ?, V = 11711(4) ?3, Dc = 3.972 g/cm3, Z = 8, μ(MoKa) = 24.661 mm?1, F(000) = 12440, the final R = 0.0527 and wR = 0.1416 for 11527 observed reflec- tions with I > 2σ(I). The crystal structure is composed of [{Cu(en)2}HPW12O40]2? anions, discrete [Cu(en)2H2O]+ complex cations and crystal water molecules, which are held together into a three- dimensional network through hydrogen-bonding interactions. The anionic [{Cu(en)2}HPW12O40]2? is formed by the mixed valance {HPWVI11WVO40}3? Keggin unit covalently linked by a {Cu(en)2}+ group.

Photocatalytic Hydrogen Evolution of Keggin-type Polyoxo-tungstates and their Electrochemical Behaviors

The photocatalytic hydrogen evolution and electrochemical behaviors of Kiggen-type XW12O40^n- （X=P, Ge and Si） are investigated. It is found that the two-electron reduced species are active for H^＋ reduction and the more negative the potential of XW12O40^（n＋2）-/（n＋1）- is, the higher the activity for hydrogen evolution is.

A Novel 3D Polyoxotungstate Constructed from Dawson Polyanions and Alkaline Earth Cations

A novel 3D polyoxotungstate [Ca（H2O）2][Ca（H2O）3]H2[P2W18O62]·9H2O（1） has been synthesized by the conventional aqueous solution method and characterized by IR spectrum,elemental analyses,single-crystal X-ray diffraction and electrochemistry.1 crystallizes in triclinic,space group P1 with a = 12.9077（14）,b = 14.8593（16）,c = 20.023（2）,α = 70.1620（10）,β = 80.8110（10）,γ = 64.3770（10）o,V = 3256.9（6）3,Z = 2,Dc = 4.790 g/cm3,μ = 31.975 mm-1,F（000） = 4080,R = 0.0412,and wR = 0.1039.X-ray single-crystal structural analysis indicates that the molecular structural unit of 1 consists of one saturated Dawson [α-P2W18O62]6-polyanion,one seven-coordinate [Ca（H2O）2]2＋ cation,one eight-coordinate [Ca（H2O）3]2＋ cation,two protons and nine lattice water molecules.Interestingly,adjacent Dawson [α-P2W18O62]6-polyanions are connected by [Ca（H2O）2]2＋ and [Ca（H2O）3]2＋ cations and hydrogen bonding interactions to form a 3D infinite framework.The electrochemistry property of 1 has been studied.

Hydrothermal Synthesis and Crystal Structure of a Novel Composite Keggin-type Arsenotungstate: [Ni(phen)_2][Hphen](AsW_(12)O_(40))

A novel polyoxometalate-based composite compound [Ni（phen）2][Hphen]（AsW12040） （phen = 1,10-phenanthroline） I has been hydrothermally synthesized and characterized by elemental analysis, IR, TGA, ESR spectroscopy and single-crystal X-ray diffraction. Each structure unit of 1 consists of one polyoxoanion AsW12O40^3-, one free phenanthroline molecule and one coordination cation [Ni（phen）2]^2＋. The title compound crystallizes in the orthorhombic system, space group F212121, with a = 12.2383（7）, b = 21.0884（11）, c = 22.3237（12） A, V= 5761.4（5） A^3, Mr = 3520.44, Z = 4, Dc = 4.059 g/cm^3, F（000） = 6204, g（MoKα） = 24.844 mm^-1, GOF = 1.022, the final R = 0.0376 and wR = 0.0742 （I 〉 2σ（I）） for 865 parameters and 9637 observed reflections with I 〉 2σ（I）.

Synthesis and Spectroscopic Characterization of Organothiophosphoryl Polyoxotungstates α-[C_6H_(11)P(S)]_2X^(n+)W_(11)O_(39)^((8-n)-)(X^(n+)P^(5+), Si^(4+), Ge^(4+), Ga^(3+)

Organothiophosphoryl polyoxotungstate derivatives α-C_6H_(11)P(S)]_2X^(n+)W_(11)O_(39)^((8-n)-)(X=P, Si, Ge, Ga) were obtained by the reactions of the monovacant α-_2X^(n+)W_(11)O_(39)^((8-n)-)(X=P, Si, Ge, Ga) were obtained by the reactions of the monovacant α-[X^(n+)W_(11)O_(39)]^((12-n)-)(X=P, Si, Ge, Ga) anions with electrophilic C_6H_(11)P(S)Cl_2 in acetonitrile. These new organic-inorganic hybrid anions were characterized by elemental analyses, IR, (()^(31)P) and (()^(183)W) NMR spectrometries. The six-line ()^(183)W NMR spectrum indicates that [C_6H_(11)P(S)]_2X^(n+)W_(11)O_(39)^((8-n)-)(X=P, Si, Ge, Ga) anions possess true C_s symmetry in acetonitrile. According to the spectroscopic observation and the chemical analyses, it is known that each of the hybrid anions consists of an α-[XW_(11)O_(39)] framework on which two equivalent C_6H_(11)P(S) groups are grafted through P-O-W bridges.

Thermal Behaviour of Some New Polyoxometalate Complexes of Ciprofloxacin with Keggin-type Heteropoly Acids

Four polyoxometalate complexes, (CPFX·HCl)_3H_4SiW_~12 O_~40 , (CPFX·HCl)_3H_3PW_~12 O_~40 , (CPFX·HCl)_3H_3PMo_~12 O_~40 and (CPFX·HCl)_4H_4SiMo_~12 O_~40 , were prepared from ciprofloxacin hydrochloride(CPFX·HCl) reacting with H_nXM_~12 O_~40 ·nH_2O(X=P,Si; M=W,Mo) in an aqueous solution, and characterized by elemental analysis, IR spectrometry and TG-DTA. The IR spectrum confirms the presence of Keggin-type anions of heteropoly acids and the characteristic functional groups of ciprofloxacin. The TG/DTA curves show that their thermal decomposition is a multi-step process including simultaneous collapse of the Keggin-type structure. At first, these compounds had a mass loss of water molecules, then several other mass losses occured due to the decomposition of ciprofloxacin hydrochloride and its fragments with the degradation of Keggin anions. The end product of decomposition is the mixture of WO_3(or MoO_3) and SiO_2(or P_2O_5), identified by X-ray diffraction and IR spectroscopy. The possible thermal decomposition mechanisms of these complexes are proposed. This study exemplified that the thermal stability of the complexes containing tungsten is much better than that of the complexes containing molybdenum.

Synthesis and Characterization of Organophosphazene Polyoxotungstate [(N_3P_3)(SiW_(11)O_(39)H_2)_3]^(12-)

A new organophosphazene polyoxotungstate, [(N3P3)(SiW11O39H2)3]12-, has been prepared by reaction of hexachlorocyclotriphosphazene with undecatungstosilicate, and characterized by elemental analysis, infrared spectroscopy, and multinuclear 31P NMR.

Synthesis and Structural Characterization of One New Polyoxotungstate Connected via Potassium Cations with aThree-dimensional Framework: H_6Na_2K_4(H_2W_(12)O_(42))Cl_2·14H_2O

One new polyoxotungstate complex H6Na2K4（H2W12O42）Cl2·14H2O 1 has been prepared in the beaker solution and characterized by elemental analysis and IR spectroscopy. Crystal data： H36Cl2K4W12Na2O56, Mr = 3411.77, monoclinic, space group P21/c, a = 11.5734（16）, b = 14.3136（19）, c = 15.459（2）A, β = 105.601（2）°, V = 2466.5（6）A^3, Z = 2, Dc = 4.594 g/cm^3, F（000） = 3008, μ = 28.447 mm^-1, R = 0.0574 and wR = 0.1239 （Ⅰ〉 2σ（Ⅰ））. Single-crystal X-ray diffraction analysis results reveal that a three-dimensional architecture in the title compound is constructed from the H2W12O42^10- units linked by potassium.

Comparison of Catalytical and Biological Activities for Substituted Polyoxotungstates Containing Ti and CpTi

The effect of the functionallization of POMs on their properties was examined by the comparison between both titanium and its corresponding cyclopentadienyl subsituted polyoxocomplexes. The polarographic half wave potential of the complexes indicated that the effect of the functionallization of POMs increased the oxidizing ability of the polyoxoanions. The inhibitory effects of the CpTi polyoxocomplexes on tumor cells are higher than those of the corresponding titanium polyoxocomplexes, and the toxicity of the former is lower than that of the latter. The oxygenation reactions of cyclohexene, styrene, trans stilbene and maleic acid with PhIO or hydrogen peroxide(30% aqueous solution) catalyzed respectively by Ti and CpTi polyoxocomplexes were compared.

A New Heteropolyoxotungstate with a Three-dimensional All-inorganic Framework [(C_2H_4N_2)_4(P_4Co_3W_4O_(28)H_6)(H_2C_2O_4)]_n

A new heteropolyoxotungstate [（C2H4N2）4（P4Co3W4O28H6）（H2C2O4）]n with a three-dimensional framework was hydrothermally synthesized.The compound crystallizes in a tetragonal system,space group I41/a with a = 17.1006（17）,b = 17.1006（7）,c = 10.7525（5）,V = 3144.2（2）3,Z = 4,Dc = 3.795 g·cm-3,F（000） = 3300,MoKα（λ = 0.71073 ）,μ = 16.460 mm-1,the final R = 0.0335 and wR = 0.0776.In the heteropolyoxotungstate,tungsten-oxygen octahedra are linked by sharing two cis-vertexes into an infinite helical chain extending along the c axis.Cobalt atoms in the octahedral geometry act as the linkers of these chains,forming a three-dimensional framework.The cobalt and phosphorus atoms in the tetrahedral geometry play a role in stabilizing the three-dimensional framework.Ethylenediamine molecules are polymerized into organic chains which locate in the interspaces of the framework in the way of interwinding with the W-O chains.

Highly Active Sulfided NiPMo Hydrodesulfurization Catalyst Prepared from Keggin-type Phosphomolybdic Acid

A highly active sulfided NiPMo/MCM-41(NiPMo-S/M41)hydrodesulfurization(HDS)catalyst was successfully synthesized using Keggin-type phosphomolybdic acid as the phosphorus and molybdenum source and thioacetamide as the sulfur source.The supported catalysts NiPMo/M41,Ni_(2)P-Mo/M41,and Ni_(2)P/M41 were also prepared to investigate the effects of Mo,S,and the Keggin structure on the HDS performance.The HDS activities of NiPMo/M41 and NiPMo-S/M41 toward dibenzothiophene were much higher than that of Ni_(2)P-Mo/M41,demonstrating that the active phases in the Keggin-structured catalysts were significantly superior to the Mo-modified Ni_(2)P phase.The HDS activities of the catalysts followed the order NiPMo-S/M41(96.7%)>NiPMo/M41(89.9%)>Ni_(2)P-Mo/M41(53.5%)>Ni_(2)P/M41(48.9%).For Ni_(2)P/M41,Ni_(2)P-Mo/M41,and NiPMo/M41,cyclohexylbenzene(CHB)was formed in low concentrations(<21.0%),indicating that direct desulfurization was the favored reaction route and that this did not change for Keggin-structured NiPMo/M41.By contrast,the CHB selectivity of NiPMo-S/M41 increased to 44.6%,much higher than that of NiPMo/M41(17.6%),demonstrating that sulfidation enhanced the hydrogenation ability,which was ascribed to a metal-acid synergistic effect.

Syntheses and Properties of Two Complexes Based on Keggin-type Polyoxometalate

Two unusual complexes [Cda（Do）4（H2O）2CI]（PW12O4O）＇2H2O （1） and [Aga（Do）6（PW12O40）][Ag（Do）2]2（PW12O4O）＇2H2O （2） were hydrothermally synthesized by the combination of two different metallic salts, Keggin-type polyoxometalate and 1,10-phen-5,6-dione （Do）, and characterized by elemental analyses, inductively coupled plasma analyses, infrared spectra, X-ray photoelectron spectroscopy, thermal gravimetry, photoluminescent spectra and single-crystal X-ray diffraction analyses. Crystal 1 is of monoclinic, space group P21/n with a = 12.383（3）, b = 18.326（4）, c = 16.437（3） A, β = 90.29（3）°, V = 3730.1（13） A3, Z = 2, CdzCasH32NsC1052PW12, Mr. = 4050.24, Dc = 3.604 g＇cm-3,μ（MoKa） = 19.145 mm1, F（000） = 3608, GOOF = 1.168, the final R = 0.0569 and wR = 0.0745 for 5715 observed reflections （1 〉 2σ（I））. Crystal 2 is of triclinic, space group Pi with a = 13.959（5）, b = 16.972（5）, c = 17.647（5）A, α = 85.970（5）, β = 81.353（5）, γ = 86.316（5）°, V = 4117（2） A3 Z = 1, Ag6C120H64N200102P2W24, Mr. = 8539.47, Dc = 3.444 g-cm-3,μ（MoKa） = 17.511 mm-1, F（000） = 3828, GOOF = 1.033, the final R = 0.0981 and wR = 0.1658 for 9906 observed reflections （I 〉 2σ（I））. Structural analyses show that complex 1 has a zero dimensional structure, which is further assembled into a one-dimensional ladder-like structure through hydrogen bonds. Complex 2 possesses a one-dimensional chain structure. Furthermore, solid-state luminescent spectra of complexes 1 and 2 indicate red and green fluorescent emission, respectively.

Rare earth inorganic-organic hybrid compounds based on Keggin-type polyoxometalate {SiW_(12)} with fast-responsive photochromism and switchable luminescence properties

Four rare earth inorganic-organic hybrid compounds based on Keggin-type polyoxometalate {SiW_(12)}with general formula [{RE(DMF)_(4)(H_(2)O)_4RE(DMF)_(6)}_(2){SiW_(12)O_(40)}_(3)](RE = La(1),Pr(2),Sm(3),Eu(4),DMF=N,N-dimethylformamide) were synthesized by the conventional solution method.Structure analyses indicate that four compounds are isostructural and are all built from three [SiW_(12)O_(40)]^(4-) polyoxoanions and DMF ligands linked by RE^(3+).Compounds 1-4 are extremely sensitive to UV light and present excellent photochromic properties,in which the coloring and fading time of samples are both no more than 2 min,and the reversible coloring-fading process can be repeated for at least 10 cycles with little fatigue,suggesting that compounds 1-4 can be a series of fast-responsive and durable photochromic materials.Moreover,the solid-state photoluminescence spectra of compounds 3(Sm) and 4(Eu)display strong characteristic emissions of rare earth ions based on f-f transitions.Meanwhile,compound4(Eu) has a longer fluorescence lifetime up to 566.74 μs.Notably,co mpounds 3(Sm) and 4(Eu) exhibit the switchable luminescence behavior induced by photochromism,which allows them to be used as potential molecular switches.

{Co_(6)}簇加成的夹心型锗钨酸盐的合成、结构及电化学性质

通过水热反应合成了一个{Co_(6)}簇加成的夹心型锗钨酸盐:[Co(dien)_(2)]{[Co(dien)(H_(2)O)]_(2)[Co(dien)]_(2)[Co_(6)(en)_(2)(μ_(3)-OH)_(2)(H_(2)O)_(6)(GeW_(8)O_(31))_(2)]}·5.5H_(2)O(1),其中dien=diethylenetriamine,en=ethylenediamine。该化合物的阴离子是一个带状{Co_(6)}簇夹心的三明治型{Co_(6)}@{GeW8}2结构。通过单晶X射线衍射、元素分析、红外光谱、粉末X射线衍射和热重实验对该化合物进行了系统性地表征。通过循环伏安测试研究了该化合物的电化学性质,同时其在电催化还原亚硝酸盐实验中展现出良好的催化活性。

多钨酸盐修饰ZrO2气凝胶催化四氢呋喃开环聚合

采用过量浸渍结合溶剂蒸发将磷钨杂多酸(TPA)分散于ZrO2气凝胶表面(TPA的质量分数为5%-45%),再经750°C空气气氛焙烧得到多钨酸盐修饰ZrO2固体酸催化剂.借助N2吸附、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、氨程序升温脱附(NH3-TPD)和吡啶吸附红外(Py-IR)光谱对催化剂的结构及酸性质进行表征,针对四氢呋喃(THF)开环聚合反应考察其酸催化性能.研究发现,TPA与ZrO2之间较强的相互作用抑制了ZrO2的晶化,同时也在一定程度上稳定了TPA的Keggin(凯金)-阴离子结构.高温焙烧的催化剂中,活性组分以ZrO2锚定的表面相(包括含有畸变或缺陷型Keggin单元的杂多酸盐及以Zr为杂原子的类杂多酸物种等)和TPA完全分解形成的氧化物体相存在,各物种的相对量取决于TPA的负载量.催化剂表面同时具有中等强度的布朗斯特德(Brnsted)酸与路易斯(Lewis)酸中心,且初始TPA负载量为20%的催化剂实现了活性组分在载体表面的单层覆盖,因而显示最大的总酸量,对THF聚合反应也表现出最高的催化活性.在反应温度为40°C、时间为20h条件下,聚合物收率达30.9%±2%,数均相对分子质量为2698±100;在催化剂重复使用6次过程中,活性未见明显降低.

用Dawson型聚氧钨酸乳液催化氧化燃油超深度脱硫

合成了Dawson型聚氧钨酸乳液催化剂Q18P2W18,Q18P2W17,和Q18P2W12.采用红外光谱和固体核磁技术对其进行了表征,并用于温和条件下H2O2氧化4,6-二甲基二苯并噻吩(4,6-DMDBT)、二苯并噻吩(DBT)、苯并噻吩(BT)和2,5-二甲基噻吩(2,5-DMT)等含硫化合物的反应中.结果表明,各催化剂的活性大小顺序为Q18P2W12>Q18P2W17>Q18P2W18.含硫化合物的氧化活性顺序为DBT>4,6-DMDBT>BT>2,5-DMT.在60oC反应30min内,Q18P2W12催化剂能够催化氧化BT完全转化成相应的砜.